Terminator Habitability: The Case for Limited Water Availability on M-dwarf Planets
Rocky planets orbiting M-dwarf stars are among the most promising and abundant astronomical targets for detecting habitable climates. Planets in the M-dwarf habitable zone are likely synchronously rotating, such that we expect significant day–night temperature differences and potentially limited fra...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2023-01-01
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| Series: | The Astrophysical Journal |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/1538-4357/aca970 |
| _version_ | 1797697250134065152 |
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| author | Ana H. Lobo Aomawa L. Shields Igor Z. Palubski Eric Wolf |
| author_facet | Ana H. Lobo Aomawa L. Shields Igor Z. Palubski Eric Wolf |
| author_sort | Ana H. Lobo |
| collection | DOAJ |
| description | Rocky planets orbiting M-dwarf stars are among the most promising and abundant astronomical targets for detecting habitable climates. Planets in the M-dwarf habitable zone are likely synchronously rotating, such that we expect significant day–night temperature differences and potentially limited fractional habitability. Previous studies have focused on scenarios where fractional habitability is confined to the substellar or “eye” region, but in this paper we explore the possibility of planets with terminator habitability, defined by the existence of a habitable band at the transition between a scorching dayside and a glacial nightside. Using a global climate model, we show that for water-limited planets it is possible to have scorching temperatures in the “eye” and freezing temperatures on the nightside, while maintaining a temperate climate in the terminator region, due to reduced atmospheric energy transport. On water-rich planets, however, increasing the stellar flux leads to increased atmospheric energy transport and a reduction in day–night temperature differences, such that the terminator does not remain habitable once the dayside temperatures approach runaway or moist greenhouse limits. We also show that while water-abundant simulations may result in larger fractional habitability, they are vulnerable to water loss through cold trapping on the nightside surface or atmospheric water vapor escape, suggesting that even if planets were formed with abundant water, their climates could become water-limited and subject to terminator habitability. |
| first_indexed | 2024-03-12T03:37:38Z |
| format | Article |
| id | doaj.art-4ca5f6bc312541bfadc0bd276fb593bc |
| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-12T03:37:38Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-4ca5f6bc312541bfadc0bd276fb593bc2023-09-03T13:07:57ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-01945216110.3847/1538-4357/aca970Terminator Habitability: The Case for Limited Water Availability on M-dwarf PlanetsAna H. Lobo0https://orcid.org/0000-0003-3862-1817Aomawa L. Shields1https://orcid.org/0000-0002-7086-9516Igor Z. Palubski2Eric Wolf3https://orcid.org/0000-0002-7188-1648University of California , Irvine Department of Physics & Astronomy, 4129 Frederick Reines Hall, Irvine, CA 92697-4575, USA ; ahlobo@uci.eduUniversity of California , Irvine Department of Physics & Astronomy, 4129 Frederick Reines Hall, Irvine, CA 92697-4575, USA ; ahlobo@uci.edu; NASA NExSS Virtual Planetary Laboratory , Seattle, WA 98195, USAUniversity of California , Irvine Department of Physics & Astronomy, 4129 Frederick Reines Hall, Irvine, CA 92697-4575, USA ; ahlobo@uci.eduNASA NExSS Virtual Planetary Laboratory , Seattle, WA 98195, USA; University of Colorado , Boulder Laboratory for Atmospheric and Space Physics, Department of Atmospheric and Oceanic Sciences, Boulder, CO 80309, USA; NASA GSFC Sellers Exoplanet Environments Collaboration , Greenbelt, MD 20771, USARocky planets orbiting M-dwarf stars are among the most promising and abundant astronomical targets for detecting habitable climates. Planets in the M-dwarf habitable zone are likely synchronously rotating, such that we expect significant day–night temperature differences and potentially limited fractional habitability. Previous studies have focused on scenarios where fractional habitability is confined to the substellar or “eye” region, but in this paper we explore the possibility of planets with terminator habitability, defined by the existence of a habitable band at the transition between a scorching dayside and a glacial nightside. Using a global climate model, we show that for water-limited planets it is possible to have scorching temperatures in the “eye” and freezing temperatures on the nightside, while maintaining a temperate climate in the terminator region, due to reduced atmospheric energy transport. On water-rich planets, however, increasing the stellar flux leads to increased atmospheric energy transport and a reduction in day–night temperature differences, such that the terminator does not remain habitable once the dayside temperatures approach runaway or moist greenhouse limits. We also show that while water-abundant simulations may result in larger fractional habitability, they are vulnerable to water loss through cold trapping on the nightside surface or atmospheric water vapor escape, suggesting that even if planets were formed with abundant water, their climates could become water-limited and subject to terminator habitability.https://doi.org/10.3847/1538-4357/aca970ExoplanetsHabitable planetsOcean planetsPlanetary atmospheresPlanetary scienceExoplanet atmospheres |
| spellingShingle | Ana H. Lobo Aomawa L. Shields Igor Z. Palubski Eric Wolf Terminator Habitability: The Case for Limited Water Availability on M-dwarf Planets The Astrophysical Journal Exoplanets Habitable planets Ocean planets Planetary atmospheres Planetary science Exoplanet atmospheres |
| title | Terminator Habitability: The Case for Limited Water Availability on M-dwarf Planets |
| title_full | Terminator Habitability: The Case for Limited Water Availability on M-dwarf Planets |
| title_fullStr | Terminator Habitability: The Case for Limited Water Availability on M-dwarf Planets |
| title_full_unstemmed | Terminator Habitability: The Case for Limited Water Availability on M-dwarf Planets |
| title_short | Terminator Habitability: The Case for Limited Water Availability on M-dwarf Planets |
| title_sort | terminator habitability the case for limited water availability on m dwarf planets |
| topic | Exoplanets Habitable planets Ocean planets Planetary atmospheres Planetary science Exoplanet atmospheres |
| url | https://doi.org/10.3847/1538-4357/aca970 |
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